Solid immersion lens array and methods for producing a solid immersion lens array

ABSTRACT

A solid immersion lens device and method of making. A solid immersion lens device is provided having a plurality of solid immersion lenses. The solid immersion lenses are provided in a predetermined pattern and secured so as to cause them to be in a fixed position with respect to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a divisional of application Serial No. 10/171,168, filedJun. 13,2002, entitled SOLID IMMERSION LENS ARRAY AND METHODS FORPRODUCING A SOLID IMMERSION LENS ARRAY, in the names of David L. Patton,et al.

FIELD OF THE INVENTION

[0002] This invention relates to an article, system and method used forcreating a solid immersion lens array.

BACKGROUND OF THE INVENTION

[0003] Recent advances in optics provide for a method of image captureon a length scale much smaller than previously realized. Such near-fieldoptical methods are realized by placing an aperture or a lens in closeproximity to the surface of the sample to be imaged. Others (see, forexample, the review by Q. Wu, L. Ghislain, and V. B. Elings, Proc. IEEE(2000), 88(9), pg. 1491-1498) have developed means of exposure by theuse of the solid immersion lens (SIL).

[0004] Typically special methods for positioning control of the apertureor lens are required, as the distance between the optical elements(aperture or lens) and the sample is extremely small. The SIL ispositioned within approximately 0.5 micrometer of the target surface bythe use of special nano-positioning technology. SIL technology offersthe advantage that the lens provides a true image capture capability.For example, features in a real object can be faithfully captured in animage of reduced spatial extent. In the case of the SIL, features can becaptured much smaller than the feature size achievable through the useof conventional or classical optics. Such conventional optics are saidto be diffraction-limited because the size of the smallest discemablefeature in an image is limited by the physical diffraction.

[0005] Due to limitations on resolutions obtainable with conventionaloptical lenses for the application such as microscopy, techniques havebeen developed to decrease the Rayleigh limit on transverse resolutionδ. The Rayleigh limit is given by (δ=0.82λ/(NA) where λ is thewavelength and NA is the numerical aperture of the focusing objective(NA=nsin (θ), where n is refractive index of the medium, and θ is theangle between the outer most rays focusing on the sample and the opticalaxis).

[0006] Coherent light such as laser light can be used to preciselycontrol the wavelength of the illumination λ. One way to decrease thetransverse resolution is to increase the index of refraction of theoptical medium, such as by the use of oil-immersion microscopy or use ofa solid immersion lens (SIL).

[0007] If an SIL is placed in contact with the sample under examination,illumination can be more readily focused on it, and use of the high NAof the system allows efficient collection of the excitation light withhigh optical transmission efficiency and observation of the sample withvery high resolution.

[0008] Methods for molding a single solid immersion lens as part of acover slide are disclosed in U.S. Pat. No. 6,301,055. Illumination of alimited field of view within a single flow channel of sample material isdescribed.

[0009] The problem is that a single solid immersion lens mounted on amicroscope or attached as an integral part of a slide cover limits thearea of view of the sample to a single location, the area directlybeneath the solid immersion lens.

[0010] Guerra et al. discloses in U.S. Pat. No. 5,910,940 a storagemedium having a layer of micro-optical lenses, each lens generating anevanescent field. They further describe in U.S. Pat. No. 6,094,413optical recording systems that take advantage of near field optics.Though recording of data is possible, the type of lenticular arraysdescribed produce an oblong or otherwise deformed or unsymmetricalpattern unsuitable for microscopy applications.

SUMMARY OF THE INVENTION

[0011] In accordance with one aspect of the present invention there isprovided a method of making a solid immersion lens device having aplurality of solid immersion lenses, comprising the steps of:

[0012] providing the plurality of solid immersion lenses in apredetermined pattern; and

[0013] securing the solid immersion lenses in the predetermined patternso as to cause them to be in a fixed position with respect to eachother.

[0014] In accordance with yet another aspect of the present inventionthere is provided a solid immersion lens device comprising:

[0015] a plurality of solid immersion lenses; and

[0016] a body portion in which the plurality of solid immersion lensesare integrally secured, the body portion having a top surface designedto engage a sample for viewing of the sample through the plurality ofsolid immersion lenses.

[0017] In accordance with yet another aspect of the present inventionthere is provided a cover slide having a plurality of solid immersionlenses integrally formed therein, the cover slide having a surfacedesigned to engage a sample for viewing of the sample through theplurality of solid immersion lenses.

[0018] In accordance with still another aspect of the present inventionthere is provided a cover slide having a plurality of solid immersionlenses integrally formed therein, the cover slide having a surfacedesigned to engage a sample for viewing of the sample through theplurality of solid immersion lenses and an open viewing area designed toengage a sample for viewing of the sample using a microscope undernormal magnification.

[0019] These and other aspects, objects, features and advantages of thepresent invention will be more clearly understood and appreciated from areview of the following detailed description of the preferredembodiments and appended claims and by reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the detailed description of the preferred embodiments of theinvention presented below, reference is made to the accompanyingdrawings in which:

[0021]FIG. 1 illustrates a schematic cross-sectional view of a singlesolid immersion lens structure made in accordance with the present art;

[0022]FIG. 2 is a schematic top view of a solid immersion lens arraymolded as part of a slide cover made in accordance with the presentinvention;

[0023]FIG. 3 is a schematic side view of a solid immersion lens array ofFIG. 2;

[0024]FIGS. 4a, 4 b and 4 c are schematic cross-sectional views of asolid immersion lens array as taken along line 4—4 of FIG. 2 along withan associated lens;

[0025]FIG. 5a illustrates a schematic cross-sectional view of yetanother solid immersion lens array made in accordance with the presentinvention;

[0026]FIG. 5b illustrates a schematic cross-sectional view of stillanother solid immersion lens array made in accordance with the presentinvention;

[0027]FIG. 6 is a schematic top plan view of yet still another solidimmersion lens array made in accordance with the present invention;

[0028]FIG. 7 is a schematic side view of a solid immersion lens array ofFIG. 6;

[0029]FIG. 8 is a schematic top plan view of another configuration of asolid immersion lens array made in accordance with the presentinvention;

[0030]FIG. 9 is a schematic side view of a solid immersion lens array ofFIG. 8;

[0031]FIG. 10 is a schematic top plan view of a combination of a solidimmersion lens array and a conventional cover slide made in accordancewith the present invention;

[0032]FIGS. 11a, 11 b and 11 c are schematic cross-sectional views of asolid immersion lens array of another embodiment of a solid immersionlens made in accordance with the present invention;

[0033]FIG. 12a is a schematic view of the eye piece/sensor of anapparatus that uses the SIL array of FIGS. 2-4;

[0034]FIG. 12b is an enlarged top plan view of the apparatus of FIG. 12aas indicated by the arrow showing the sample being viewed;

[0035]FIG. 13a is a schematic view of the eye piece/sensor of anapparatus of another embodiment of the present invention; and

[0036]FIG. 13b is an enlarged top plan view of the apparatus of FIG. 13aas indicated by the arrow showing the sample being viewed.

DETAILED DESCRIPTION OF THE INVENTION

[0037] The invention has been described in detail with particularreference to certain preferred embodiments thereof, but it will beunderstood that variations and modifications can be effected within thescope of the invention.

[0038] Referring to FIG. 1, there is illustrated a cross-sectional viewof a functioning solid immersion lens (SIL) 10 made in accordance withthe present art, with indications of the parameters used to describe thestructure and operation. A solid immersion lens portion 15 comprises atruncated sphere of radius r and an index of refraction n_(s). It isdisposed at a highest height h above a surface 20 of a body portion 25so that a boundary margin 30 is formed which is narrower in diameterthan the diameter of the lens (2r) portion 15. An observation region 35is provided at a distance h′ from the surface 20. The constraint heighth is given by the following relation:

r(1−cos φ)<h<r+r/n _(s)

[0039] where

[0040] r is the radius of the sphere,

[0041] h is the height of the layer,

[0042] φ is the polar angle from the center of the sphere to the edge ofthe orifice formed by the undercut margin,

[0043] n_(s) is the index of refraction of the material, which forms thelens.

[0044] The region 35 comprise the area between the top surface 40 of aslide 45 and the surface 47 which is h′ below surface 20. The thicknessh′ above the surface 20 is given by the relation:

h′=r+(r/n _(s))−h.

[0045] Samples 37 are placed in the region 35 between the top surface 40of the slide 45 and the bottom surface 47 of the body portion 25 forobservation according to the intended application, such as microscopy,spectroscopy, or cytometry as is well known to those skilled in the art.The body portion 25 can also serve as a slide cover 27. Also shown withthe SIL 10 is a collecting/collimating lens 50. The spherical structureand collection configuration admits to construction of lens systemshaving a numerical aperture higher than unity, which is particularlyuseful for ultra sensitive spectroscopy, high lateral resolutionimaging, and finite depth of field imaging. A method for producing a SILis disclosed in U.S. Pat. No. 6,301,055.

[0046]FIG. 2 illustrates a top view of a solid immersion lens array 55formed by molding a plurality of solid immersion lens portion 15 of theSIL 10 in a fixed position to one another as part of the slide cover 27made in accordance with the present invention. As previously discussedin FIG. 1 like numerals indicate like parts and operations. The numberand spacing of the solid immersion lens portion 15 can be made to suitthe type of sample, which is to be observed. The type of material usedto form the solid immersion lens array 55 depends on various parameters.The method disclosed in U.S. Pat. No. 6,301,055 for molding a single SILlists suitable materials as low temperature of formation polymers, roomtemperature vulcanization elastomers, low temperature of formationepoxies, polyimides, polycarbonates, and photo resists, or pliantsilicone elastomers,

[0047] Optical performance of the elements of the array is related tothe index of refraction n_(s) of the material forming the lens. Theability of the lens to reduce spot size as noted above, is inverselyproportional to n_(s); therefore it is highly desirable to work withlens materials with large indices of refraction. Commonly used glassesfor lens manufacture range in index of refraction from about 1.49 to1.85. However there are specialty glasses with much higher indices.Plastic materials tend to have low indices of refraction, therefore theyare less desirable for SIL manufacture. Thus it is desirable that theindex of refraction be equal to or greater than 1.49 for the SIL array.Another consideration in lens material is the ability to withstand thetemperatures required for molding and the ability to interactappropriately with the mold material. A method for creating SIL arraysusing glass is described in FIG. 5a.

[0048]FIG. 3 illustrates a side view of a solid immersion lens array 55formed by molding the solid immersion lens portion 15 of the SIL 10 aspart of the slide cover 27 made in accordance with the presentinvention. As previously discussed in FIG. 1 like numerals indicate likeparts and operations.

[0049] Referring to FIG. 4a, there is illustrated a cross-sectional viewof a solid immersion lens array 55 as taken along line 4—4 of FIG. 2along with an associated lens made in accordance with the presentinvention. As previously discussed in FIG. 1 like numerals indicate likeparts and operations. In the embodiment shown in FIG. 4a, a plurality ofsolid immersion lens portion 15 are molded with a body portion 25 toform an array as part of a slide cover 27. The solid immersion lensarray 55 allows the user to move a magnifying imaging device 60 (seeFIG. 12a) collecting/collimating lens 50 in an x and z direction todifferent positions as shown in FIGS. 4b and 4 c to observed differentlocations of the sample 35 shown in FIG. 1.

[0050] The present embodiment describes a plurality of solid immersionlens portions 15 integrally formed with the body portion 25 to form thesolid immersion lens array 55. In another embodiment of the presentinvention referring to FIG. 5a, there is illustrated a cross-sectionalview of a solid immersion lens array 100 made in accordance with thepresent invention. The solid immersion lens array 100 is made by placingglass spheres 101 and 102 in a fixed position with their edges touching.The spheres 101 and 102 are rigidly attached to each other by via aconnecting member 110. The connecting member 110 can be formed using anadhesive such as OP29 manufactured by the Dymax Corporation. The SILarray is completed by grinding a flat surface 115 on the connectedspheres 101 and 102. forming SIL 104 and SIL 105. The method of grindinga flat on a glass sphere is well known to those skilled in the art. Inanother method shown in FIG. 5b, the SIL array 100 is created by formingadjacent SIL's 104, 105 and a connecting member 113 as an integral part.In both methods an observation region 35 is provided at criticaldistance f; as is well known to those skilled in the art. Theobservation region 35 comprises the area at the distance f, for example0.5 micrometers below surface 115 of the SIL and the top surface 40 of aslide 45. Samples 37 to be observed are placed in the observation region35 according to the intended application, such as microscopy,spectroscopy, or cytometry as is well known to those skilled in the art.Alternatively, individual spherical or truncated spherical lens elementsmay be bonded to the body portion 25 to create the array. In this case,the adhesive must be index matched to both the body and the sphericalelements so as to not degrade the imaging properties of the array. Thebonding can be performed using an index matching adhesive such as OP29manufactured by the Dymax Corporation. Spheres made of materials havingdifferent indices would allow for different magnifications.

[0051]FIG. 6 illustrates a top view of the embodiment of the solidimmersion lens array 100 shown in FIGS. 5a and 5 b. In this embodimentthe solid immersion lens array 100 is formed by connecting adjacentSIL's 104, 105, 106, 107, 108, and 109 by the connecting member 110 or113 described in FIGS. 7a and 7 b respectively made in accordance withthe present invention. As previously discussed in FIGS. 5a and 5 b likenumerals indicate like parts and operations. Multiple columns 111 androws 112 of SIL 104 can be created using this technique. The number andspacing of the solid immersion lens 104 can be made to suit the type ofsample, which is to be observed.

[0052]FIG. 7 illustrates a side view of the embodiment of the solidimmersion lens array 100 shown in FIG. 6.

[0053]FIG. 8 illustrates a top view of another configuration the solidimmersion lens array 100 shown in FIG. 6 made in accordance with thepresent invention. As previously discussed in FIG. 6 like numeralsindicate like parts and operations. Multiple columns 111 and rows 112 ofSIL 104 can be created using this technique. The number and spacing ofthe solid immersion lens 104 can be made to suit the type of sample,which is to be observed. In this case, a close-packed array of sphericalcomponents is described.

[0054]FIG. 9 illustrates a side view of the solid immersion lens array100 configuration shown in FIG. 8.

[0055]FIG. 10 illustrates a top plan view of a combination of a solidimmersion lens array 55 and a conventional cover slide 27 made inaccordance with the present invention. As previously discussed in FIG. 2like numerals indicate like parts and operations. The number and spacingof the solid immersion lens portion 15 can be made to suit the type ofsample, which is to be observed. An open viewing area 120 is provided,which permits the user to observe the sample 37 (see FIG. 1) using theimaging device 60 such as a microscope under normal magnification orthrough the solid immersion lens portion 15 at increased spatialresolution.

[0056] Referring to FIG. 11a, there is illustrated a cross-sectionalview of a solid immersion lens array 130 made in accordance with thepresent invention. As previously discussed in FIG. 4a like numeralsindicate like parts and operations. In the embodiment shown in FIG. 11athe solid immersion lens portions 15 are molded with the body portion25. A channel 132 is formed as part of the body portion 25 and connectedto a pumping mechanism (not shown) via tubes 136 and 137. The method forforming the channel 132 and for pumping a sample 135 through the channel132 is described in U.S. Pat. No. 6,301,055. The solid immersion lensarray 130 allows the user to move the magnifying imaging device 60 (seeFIG. 12a) collecting/collimating lens 50 in an x and z direction toobserve different locations along the channel 132 as shown in FIGS. 11band 11 c to observed different portions of the sample 135, which hasbeen pumped into the channel 132. Referring now to FIG. 12a, the sample37 can be viewed and an image captured using the solid immersion lensarray 55 and a magnifying imaging device 60 such as a microscope. Alight beam 62 from a light source 64 reflects from a beam splitter 66and passes through the collecting/collimating lens 50 of conventionaldesign and impinges onto the solid immersion lens portion 15 of thesolid immersion lens array 55. Samples 37 to be observed are placed inthe region 35 between the top surface 40 of the slide 45 and the bottomsurface 47 of the body portion 25 of the solid immersion lens array 55as is well known to those skilled in the art. The light beam 62 isreflected from the sample 37, passes through the solid immersion lensarray 55, the lens 50, and the beam splitter 66, imaging the sample 37onto a sensor/eye piece 78 by a lens system 80. The sensor 78 can be aCCD or similar type device. The slide 45 with the solid immersion lensarray 55 is located on an x, y, z, and θ translation device 68. The x,y, z, and θ translation device 68 can also contain an additional lightsource 70 whose light beam 72 can be directed to illuminate the slide 45and sample 37 from underneath. The collecting/collimating lens 50 ispositioned in relation to the solid immersion lens array 55 by an x, y,z, and θ translation device 74. Both translation (positioning) devices68 and 74 and sensor 78 are connected to and controlled by a logic,control and memory unit 76. The light source 72 can be used in place ofor in addition to the light source 64. The light sources 64 and 72 canbe chosen and filters (not shown) can be added to the light path toprovide illumination of a specific wavelength. The light sources 64 and72 can be lasers or other types of illumination such as UV, IR etc canbe used, as appropriate for the type of lens material used.

[0057] Referring now to FIG. 12b, an enlarged partial view of the imageof the sample 37 captured by the device 60 is shown. Using the imagingdevice 60, images of the sample 37 are displayed for viewing. Inaddition to observing the sample 37 via a sensor 78 and electronicdisplay (not shown) the sample 37 can be viewed by the human eye 90using a standard microscope eyepiece 85.

[0058]FIG. 13a illustrates another embodiment of the present invention.The sample 37 can be viewed and an image captured using the solidimmersion lens array 100 using a magnifying imaging device 60 such as amicroscope. A light beam 62 from a light source 64 reflects from a beamsplitter 66 and passes through the collecting/collimating lens 50 ofconventional design and impinges onto the solid immersion lens portions104, 105, 106, 107, 108 and 109 which represent several of the solidimmersion lens portions of the solid immersion lens array 100. Samples37 to be observed are placed between the top surface 40 of the slide 45and the bottom surface 47 of the solid immersion lens portions 104, 105,106, 107, 108 and 109 of the solid immersion lens array 100 as is wellknown to those skilled in the art. The light beam 62 is reflected fromthe sample 37, passes through the solid immersion lens array 100, thelens 50, and the beam splitter 66, imaging the sample 37 onto asensor/eye piece 78 by a lens system 80. The slide 45 is located on anx, y, z, and θ translation (positioning) device 68. The x, y, z, and θtranslation device 68 can also contain an additional light source 70whose light beam 72 can be directed to illuminate the slide 45 andsample 37 from underneath. The collecting/collimating lens 50 and thesolid immersion lens array 100 are positioned in relation to each otherand to the slide 45 by an x, y, z, and θ translation devices 74, 77, 79and x, y, z, and θ translation device 68. The translation devices 68,74, 77 and 79 and sensor/eye piece 78 are connected to and controlled bya logic, control and memory unit 76. The light source 72 can be used inplace of or in addition to the light source 64. The light sources 64 and72 can be chosen and filters (not shown) can be added to the light pathto provide illumination of a specific wavelength. Lasers or other typesof illumination such as UV, IR etc can be used for the light sources 64and 72. Again, the lens material must be appropriately transmissive foruse in a particular region of the spectrum.

[0059] Referring now to FIG. 13b, an enlarged partial view of the imageof the sample 37 captured by the device 60 is shown. Using the imagingdevice 60, images of the sample 37 are displayed for viewing. Inaddition to observing the sample 37 via a sensor/eye piece 78 andelectronic display (not shown) the sample 37 can be viewed via the humaneye 90.

[0060] It is to be understood that various changes and modificationsmade be made without departing from the scope of the present invention,the present invention being defined by the claims that follow. PARTSLIST 10 solid immersion lens (SIL) 15 solid immersion lens portion 20surface 25 body portion 27 cover slide 30 margin 35 observation region37 sample 40 top surface 45 slide 47 bottom surface 50collecting/collimating lens 55 solid immersion lens array 60 magnifyingimaging device 62 light beam 64 light source 66 beam splitter 68translation device 70 light source 72 light beam 74 translation device76 logic, control and memory unit 77 translation device 78 sensor/eyepiece 79 translation device 80 lens system 85 eyepiece 90 eye 100 solidimmersion lens array(SIL) 101 sphere 102 sphere 104 solid immersion lens(SIL) 105 solid immersion lens (SIL) 106 solid immersion lens (SIL) 107solid immersion lens (SIL) 108 solid immersion lens (SIL) 109 solidimmersion lens (SIL) 110 connecting member 111 column 112 row 113connecting member 115 flat surface 120 open viewing area 130 solidimmersion lens array 132 channel 135 sample 136 tube 137 tube

What is claimed is:
 1. A method of making a solid immersion lens devicehaving a plurality of solid immersion lenses, comprising the steps of:providing said plurality of solid immersion lenses in a predeterminedpattern; and securing said solid immersion lenses in said predeterminedpattern so as to cause them to be in a fixed position with respect toeach other.
 2. A solid immersion lens device comprising: a plurality ofsolid immersion lenses; and a body portion in which said plurality ofsolid immersion lenses are integrally secured, said body portion havinga top surface designed to engage a sample for viewing of said samplethrough said plurality of solid immersion lenses.
 3. A solid immersionlens device according to claim 2 wherein there is said plurality ofsolid immersion lenses are provided in a row.
 4. A solid immersion lensdevice according to claim 3 wherein there is provided a plurality ofadjacent rows.
 5. A solid immersion lens device according to claim 4wherein said plurality of rows are aligned so as to provide a pluralityof rows and columns of solid immersion lenses.
 6. A cover slide having aplurality of solid immersion lenses integrally formed therein, saidcover slide having a surface designed to engage a sample for viewing ofsaid sample through said plurality of solid immersion lenses.
 7. A solidimmersion lens device according to claim 6 wherein there is saidplurality of solid immersion lenses provided in a row.
 8. A cover slideaccording to claim 7 wherein there is provided a plurality of adjacentrows.
 9. A cover slide according to claim 7 wherein said plurality ofrows are aligned so as to provide a plurality of rows and columns ofsolid immersion lenses.
 10. A cover slide according to claim 6 whereinsaid plurality of solid immersion lenses have an index of refractionequal to or greater than 1.49.
 11. A cover slide according to claim 6wherein said plurality of solid immersion lenses have an index ofrefraction in the range of about 1.49 to about 1.85.
 12. A cover slideaccording to claim 6 wherein said plurality of solid immersion lensesare made of glass.
 13. A cover slide having a plurality of solidimmersion lenses integrally formed therein, said cover slide having asurface designed to engage a sample for viewing of said sample throughsaid plurality of solid immersion lenses and an open viewing areadesigned to engage a sample for viewing of said sample using amicroscope under normal magnification.